Plate-type nuclear fuel element



Jan.;10; 1967 N. c. JESSEN ETAL 3,297,543

PLATE-TYPE NUCLEAR FUEL ELEMENT Filed July 7, 1964 FIG. 1

FIG.3

INVENTORS Nicholas C. Jessen By W|ll|am F. Heer ATTORNEY Whitedf StatesPatent This invention relates to plate-type nuclear fuel elements andmore particularly, to such elements in which the fissile core materialis arranged within a circumscribing frame member and encased by coverplates.

Inthe past it has been standard practice to manufacture uranium-aluminumalloy fuel plates by inserting the fissile core material into a framemember, cladding or covering both sides of the frame member and the corewith plates, and roll bonding the assembly. However, one

, serious disadvantage stemming from the use of uraniumaluminum :alloyas thefuel has been its lack of homogeniety gwiththe consequentpossibility of developing hot spots in the fuel plates. Thisnecessitates reduction in the heat. output rate, and a correspondingreduction in the eflicjiency potential. Further, in such plate-typeelements,

, as the uranium content of the alloy is increased, the workability ofthe core, particularly in the rolling operation, decreases. rapidly andposes a difficult manufacturing problem. This problem isfurtheraggravated if boron is added :to the fuel alloy because itstendency to segregate is worse than that of uranium. To date it has beenvery diflicult to attain any degree of homogeneity inboronaluminum-uranium fuel alloys.

Toovercome this problem, a cermet, such as powdered aluminum. metal anduranium oxide, has been suggested as thefuel material. However, thepowdered fuel, though satisfying the need for a homogeneous mass, has atendency to squirt out of its frame member when pressure is appliedduring the roll bonding step in the assembly. This j is known asstringering and results in the dispersion of fuel outside of the desiredlocation within the plate.

Itisa primary object of the present invention to provide .a plate-typefuel element construction which overcomes the objections just cited byassuring that the cermet core will remain intact and will be properlypositioned within theelement.

Accordingly, the present invention provides a circumscribing framemember having an aperture extending between "its oppositely disposedfaces. In the aperture a fuel core is positioned so that it is recessedwith respect to both the upper and lower faces of the frame member. Corecover plates are fitted to and are in contact with the upper. and lowersides of the core, within the aperture. They are of a thickness suchthat they will be flush with the adjacent upper and lower faces of theframe member.

Next, a cover plate is placed on the upper and lower faces of the framemember covering its entire surface. The assembled: fuel element is thenrolled to assure bonding between its various components.

.The core cover plates may be integrally attached to the framegmember,as by welding, prior to placing of the upper. and lower cover plates, toassure the maintenance of the core withinthe aperture.

Preferably, the fuel core comprises a cermet consisting of powderedaluminum metal and uranium oxide and in some instances, if required,boron.

The various features of novelty which characterize this invention arepointed out with particularity in the claims 3,297,543 Patented Jan. 10,1967 Of the drawings:

FIG. 1 is an exploded perspective view of the fuel element embodying thepresent invention;

SIG. 2 is a perspective View of the assembled element; an

FIG. 3 is a cross section taken along line 33 in FIG. 1.

In FIG. 1 the various components of a plate-type fuel element 10 areillustrated in disassembled, exploded fashion, while assembly views areshown in FIGS. 2 and 3. Forming the center layer of the fuel element 10is a rectangular frame member 12 having a rectangular aperture 14extending through it between its upper and lower faces 16 and 18respectively. This aperture accommodates a fuel core 20 of a thicknessrelative to the frame 12 so that it may be positioned recessed from boththe upper and lower faces 16, 18 of the frame member. Additionally, theaperture accommodates a pair ofcore cover plates 21, 22 which cover theupper and lower faces, respectively, of fuel core 20. These core coverplates are of a thicknesssuch that upon assembly of the components, theywill be flush with the corresponding faces 16, 18 of the frame member12. To prevent any displacement of the fuel core material from withinthe aperture, the core cover plates are welded about their periphery tothe frame member.

Cover plates 23, 24 are provided for the upper and lower faces 16, 18,respectively, of the frame member 12, and the component assembly is thenrolled to achieve bonding between the various cover plates and the framemember and to further compact the fuel core.

As mentioned previously, one of the problems faced in employing cermetsis the possibility that the cermet core under pressure of rolling mightsquirt into the interfaces between the frame member and its coverplates. By utilizing core cover plates and welding them to the framemember, the retention of core material within the aperture is assured.This feature is especially important since proper location of the fuelis essential to the efficient use of fuel elements.

It will be appreciated that it would be equally advantageous to use corematerials other than cermets in the construction disclosed by thepresent invention to achieve plate-type fuel elements in which the fuelis retained within a definite location.

Tests have indicated that both U 0 as well as U0 may be employed in thecermet, and there is some indication that the use of U 0 powder might bepreferable in the present invention. Additionally, the present inventionwould be applicable for any powder metallurgy fuel cores.

While in accordance with the provisions of the statutes the inventionhas been illustrated and described in the best form and mode ofoperation of the invention now known, those skilled in the art willunderstand that changes may be made in the form of the apparatusdisclosed without departing from the spirit of the invention covered 'bythe claims, and that certain features of the invention may sometimes beused to advantage without a corresponding use of other features.

What is claimed is:

1. A plate-type fuel element comprising:

(A) a frame member having a pair of oppositely disposed faces and anaperture in at least one of said faces,

(B) a core of fissile material disposed within said aperture andrecessed from said face containing the aperture, the edges of said corebeing in substantial contact with the sides of said aperture, and

(C) a core cover plate superimposed upon said core and disposed withinand filling said aperture.

2. A plate-type fuel element as set forth in claim 1 wherein the corecover plate is integrally attached to the frame member sealing the corewithin said aperture.

3. A plate-type fuel element comprising:

(A) a frame member having a pair of oppositely disposed faces and anaperture in at least one of said faces,

(B) .a core of fissile material having a thickness less than said framemember disposed within said aperture and recess from said facecontaining the aperture, the edges of said core being in substantialcontact with the sides of said aperture,

(C) a core cover plate superimposed upon said core within said apertureand the edges of said core cover plate being in substantial contact withthe sides of said aperture, and

(D) a frame member cover plate superimposed upon the face of said framemember having the aperture therein.

4. A plate-type element comprising:

(A) a frame member having a pair of oppositely disposed faces and anaperture extending therethrough between said faces,

(B) a core of fissile material having a thickness less than said framemember disposed within said aperture .and recessed from both faces ofsaid frame member, the edges of said core being in substantial contactwith the sides of said aperture,

(C) a core cover plate superimposed on each side of said core withinsaid aperture and the edges of said core cover plate being insubstantial contact with the sides of said .aperture, and

(D) a frame member cover plate superimposed upon each face of the framemember.

5. A plate-type fuel element comprising:

(A) a relatively thin frame member having a pair of oppositely disposedfaces and a rectangular shaped aperture extending therethrough betweensaid faces,

(B) a core of fissile material having a thickness less than said framemember disposed within said aperture and recessed from both faces ofsaid frame member, the face of said core having the same dimensions andshape as said aperture and the edges of said core being in substantialcontact with the sides of said aperture,

(C) a core cover plate having substantially the same face dimension andshape as said aperture and disposed therein on each face of said core,and

(D) a frame member cover plate superimposed upon each face of said framemember and said assembled fuel element rolled to provide bonding of theseparate components.

6. A plate-type fuel element as set forth in claim 5 wherein the outerfaces of said core cover plates are arranged flush with thecorresponding faces of said frame member and are integrally attachedthereto.

References Cited by the Examiner UNITED STATES PATENTS BENJAMIN R.PADGETT, Primary Examiner. L. DEWAYNE RUTIJEDGE, Examiner. I. V. MAY, M.J. SCOLNICK, Assistant Examiners.

1. A PLATE-TYPE FUEL ELEMENT COMPRISING: (A) A FRAME MEMBER HAVING APAIR OF OPPOSITELY DISFACES, (B) A CORE OF FISSILE MATERIAL DISPOSEDWITHIN SAID APERTURE AND RECESSED FROM SAID FACE CONTAINING THEAPERTURE, THE EDGES OF SAID CORE BEING IN SUBSTANTIAL CONI TACT WITH THESIDES OF SAID APERTURE, AND